Patent GB-1182839-A (GB)
Title: Thin Film Magnetic Device.
IPC: G11C7/02
Filed: 1967-08-01
Abstract: 1,182,839. Magnetic storage apparatus. INTERNATIONAL BUSINESS MACHINES CORP. 1 Aug., 1967 [4 Aug., 1966], No. 35212/67. Heading H3B. [Also in Division H1] In a magnetic anisotropic thin film memory device 2 information stored in the device is read out by sensing the variation in absorption of an R.F. signal applied to a sense line 12 arranged perpendicular to the cary axis 22 of the film due to the film when the magnetization of the film is varied along its easy axis by a pulse on a perturb line 27 arranged perpendicular to the sense line. The sense line 12 is surrounded by a closed hard axis loop film 3, 4, 5, 6 and is connected at one end to an R.F. source 18 and at the other end to a diode detector 20. Arranged perpendicular to the sense line 12 is a perturb line 27 along which line a pulse is passed which generates a magnetic field parallel to the easy axis 22 of the film. In operation the R.F. signal from source 18 generates a magnetic field perpendicular to the easy axis 22 and since the frequency of the R.F. signal is partially in resonance with the electrons in the thin film structure the signal is partially absorbed in the film. Depending on whether a "]" or "0" is stored, represented by the vectors 24, 26 along the easy axis the perturb field due to the pulse on the line 27 is either parallel or antiparallel to the vectors 24, 26 and hence the amount of absorption varies, Fig. 2 (not shown), and increases if a binary "1" is stored and decreases if a binary "0" is stored, Figs. 6a. 6b (not shown). The read out is non-destructive and the output signal at detector 20 increases with increase of disturb pulse and has a longer pulse width for longer perturb pulses. A plurality of the devices 2 may be arranged in a matrix, Fig. 8, in which the coupled hard axis structures 2 are shown as continuous elements rather than discrete ones. Information is written into the store as described in Specification 1,182,840. 1,182,840. Thin film magnetic stores. INTERNATIONAL BUSINESS MACHINES CORP. 2 Aug., 1967 [4 Aug., 1966], No. 35404/67. Heading H3B. [Also in Division H1] In order to write information into an anisotropic thin film microwave absorption memory of the type shown in Specification 1,182,839, a substantially hard axis magnetic field is applied along each column and a substantially easy axis magnetic field is applied along each row. The matrix, Fig. 1, comprises a plurality of continuous closed hard axis loop thin film structures 2 each enclosing a sense line 10 connected at one end to a microwave source 6 and a sense amplifier detector. In order to write information into the store a plurality of word drivers 20 are each connected to drive lines 22 arranged generally parallel to the hard axis of the films as shown and a plurality of driver circuits 26, which supply bit pulses of lesser intensity than the word drivers 20 are connected to bit lines 28 which extend generally parallel to the easy axis and are looped back. Each driver line 28, Fig. 2, comprises an upper leg 28a and a lower leg 28b each leg comprising a plurality of lands 36 in the shape of a parallelogram and the lands being interconnected by links 45, 46. In operation a bit current flowing from top to bottom is represented by a vector which has a component parallel to the easy and to the hard axis of the films and since the drive line is looped back upon itself the current now flows from the bottom of the Figure to the top which current has a vector along the easy axis which cancels out that due to the current in the upper leg 28a and a vector along the hard axis which adds to that of the upper leg. The resultant of the current flowing in the bit line 28 is to provide a magnetic field along the easy axis. At the same time a current is passed through the appropriate word driver line 22 which line is directed along the easy axis and hence a field is produced parallel to the hard axis. When the pulses cease the resultant magnetization of the film takes up one or the other of the positions along the easy axis determined by the binary digit stored therein.